CHEMICAL SENSING SYSTEM AND METHOD

• US 20090236528A1
• Filed: 01/29/2009
• Published: 09/24/2009
• Est. Priority Date: 09/22/2003
• Status: Active Grant

• Current Assignee: CeLight, Inc.
• Original Assignee: CeLight, Inc.
• Inventors: Kaplan, Arkady, Shpantzer, Isaac, Khurgin, Jacob, Achiam, Yaakov, Cho, Pak Shing
• Granted Patent: US 8,009,294 B2
• Time in Patent Office: Days
• US Class Current: 250/339.70
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0205 Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/45 Interferometric spectrometry
• CPC Class Codes: G01J 9/04 by beating two waves of a same source but of different frequency and measuring the phase shift of the lower frequency obtained
• CPC Class Codes: G01N 2021/1793 Remote sensing
• CPC Class Codes: G01N 2021/655 Stimulated Raman
• CPC Class Codes: G01N 21/171 with calorimetric detection, e.g. with thermal lens detection
• CPC Class Codes: G01N 21/636 using an arrangement of pump beam and probe beam; using the measurement of optical non-linear properties; non-linear optics per se G02F1/35
• CPC Class Codes: G01N 21/65 Raman scattering
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00

Abstract

A photo-thermal, interferometric spectroscopy system is disclosed that provides information about a chemical, such as explosives and the like, at a remote location. It may be used for solid residue detection on a surface. The system includes a novel light detector system with a matrix of optical elements focusing portions of a received light beam on input waveguides of an optical combiner. The combiner adjusts the phases of the received beam portions and combines them together to maximize the intensity of an output beam. The output beam is detected by a detector, and information about at least one of, absorption spectrum and concentration of the chemical is recovered. In the preferred embodiment the detector is a coherent detector based on 90-degrees optical hybrid.

Claims

1. A photo-thermal interferometric spectroscopy system that provides information about a chemical at a remote location, comprising:

a light detector system positioned remotely from the chemical, the detector system having a matrix of optical elements focusing portions of a received light beam on input waveguides of an optical combiner;

the combiner adjusting the phases of the received beam portions and combining them together, wherein the phases of the beam portions are adjusted to maximize the intensity of an output beam;

a detector detecting the output beam; and

a digital signal processing unit, connected to the detector, recovering information about at least one of, absorption spectrum and concentration of the chemical.

2. The system of claim 1, further comprising:

a first light source assembly that emits a first beam, the first beam having one or more wavelengths that interact with the chemical and change a refractive index of the chemical;

a second laser that produces a second beam, the second beam interacting with the chemical with changed refractive index forming a third beam;

the third beam forming the received light beam.

3. The system of claim 2, wherein the first light source beam generates a spectrum of wavelengths in at least one of the near, mid and far infrared ranges.

4. The system of claim 3, wherein the first light source wavelengths are tunable.

5. The system of claim 2, wherein the first light source beam consisting of two beams with two different wavelengths that results in stimulated Raman absorption in the chemical.

6. The system of claim 5, wherein the Raman absorption is in 6-8 micron range.

7. The optical system of claim 2, wherein the second laser is a pulsed light source.

8. The system of claim 1, wherein:

the detector including a coherent receiver having a 90-degrees optical hybrid connected to at least two balanced photodetectors.

9. The optical system of claim 8, wherein the detector system provides homodyne detection of the light beam passed through the chemical.

10. The system of claim 1, wherein the chemical is in the form of a gas, liquid or solid.

11. The system of claim 1, wherein the chemical is a solid residue on a surface.

12. The system of claim 1, wherein the chemical is at an explosive site, a site of pollution and a site of a chemical weapon.

13. The system of claim 1, wherein the beam combiner comprising:

2^M input waveguides, where M is integer ≧

2, receiving portions of the optical beam;

(2^M−

1) couplers;

each coupler is formed by two waveguides, coming in and out of the coupler;

in each coupler one output waveguides is used in control means for changing an input phase of the optical beam portion in the same waveguide before its coupling;

one output waveguide forming an input waveguide for a consequent coupler from (2^M−

1) couplers;

an output waveguide from the last coupler forming an output beam of the device; and

wherein the control means changing the input phases to maximize the output beam energy.

14. The optical system of claim 13, wherein the combiner is a device selected from at least one of, an integrated device, a free-space optical link device, and a fiber optics device.

15. The optical system of claim 1, wherein the remote location is selected from, a standoff location, outside of a blast range, inside a blast range, and at an entry point.

16. A method for determining information about a chemical at a remote location, comprising:

receiving at least a part of a light beam passed through the chemical;

compensating phase distortions in the light beam passed through the chemical by adjusting portions of the received beam using a beam combiner;

detecting an output signal from the beam combiner and measuring a phase shift of the light beam being indicative of at least one of, absorption spectrum and concentration of the chemical.

17. The method of the claim 16, wherein

the chemical is a solid residue on a surface.

18. The method of the claim 16, further comprising:

illuminating the chemical with a strobe beam having two beams with different wavelengths resulting in stimulated Raman absorption in the chemical;

illuminating the chemical with a probe beam, the probe beam passing through the chemical.

19. The method of the claim 16, further comprising:

detecting an output signal from the beam combiner using a coherent detector with 90-degrees optical hybrid.

20. The method of the claim 16, wherein the beam combiner comprising:

2^M input waveguides, where M is integer ≧

2, receiving portions of the optical beam;

(2^M−

1) couplers;

each coupler is formed by two waveguides, coming in and out of the coupler;

in each coupler one output waveguides is used in control means for changing an input phase of the optical beam portion in the same waveguide before its coupling;

one output waveguide forming an input waveguide for a consequent coupler from (2^M−

1) couplers;

an output waveguide from the last coupler forming an output beam of the device; and

wherein the control means changing the input phases to maximize the output beam energy.